From June 1987 to July 1992, computed tomography or magnetic resonance imaging was performed in 182 spinal fractures. Among them, burst fractures were 55 cases. We calculated the stenotic ratios of the area occupied by the retropulsed bony fragments to the estimated area of the original spinal canal. Neurologic status of 55 consecutive patients with thoracic, thoracolumbar, lumbar burst fractures was correlated with the amount of neural canal encroachment demonstrated by CT or MRI. The following results were obtained. l. In the location, Tl 1 and T12 were 20 cases, Ll was 16 cases, L2 and below were 19 cases. 2. Burst fractures having the following ratios are at significant risk of neurologic involvement: at Tll and T12 with 38.4% or more, at Ll with 47.5% or more, and at L2 and below with 57.6% or more. 3. Degree of spinal canal narrowing and degree or neurological impairment is correlated in thoracic and lumbar burst fractures.